Clinicopathological features of 45,X/46,Xidic(Y) mosaicism and therapeutic implications: case report.

CONTEXT 45,X/46,Xidic(Y) mosaicism demands careful and thorough study because of both its variable clinical features and its potential complications. CASE REPORT The present case relates to a three-year-old girl with the mosaic karyotype 46,X,idic(Y)(q11.2)[23]/45,X[6]. She had no signs of virilization or Turner's syndrome phenotype, but she was referred to our hospital because she presented reduced growth rate, abnormal facies and a melanotic nevus. After examination, she underwent prophylactic gonadectomy because of the risk of gonadoblastoma. Cytogenetic analysis on the streak gonads and blood showed significant differences in the 45,X cell line between these two tissues. The presence of the sex-determining region Y (SRY) gene did not determine male differentiation, which meant in the present case that the predominance of the X cell line in the gonadal tissue was probably due to the determining factor for female sexual differentiation.